abstractsolver.java

一个关于java 的常用工具包

package org.jutil.math.matrix;

/**
 * <p>A helper class for classes that solve systems of equations using
 *    matrices. That often involves solve a triangular system at the end.</p>
 *
 * @path    $Source: /cvsroot/org-jutil/jutil.org/src/org/jutil/math/matrix/AbstractSolver.java,v $
 * @version $Revision: 1.3 $
 * @date    $Date: 2002/07/02 14:27:31 $
 * @state   $State: Exp $
 * @author  Marko van Dooren
 * @release $Name:  $
 */
public abstract class AbstractSolver {
	
	/**
	 * <p>Solve the uppertriangular linear system of equations defined by
	 * <code>R * x = b</code></p>
	 *
	 * @param R
	 *        The uppertriangular matrix containing the coefficients of the
	 *        equations.
	 * @param b
	 *        A column containing the right-hand sides of the equations.
	 */
 /*@
	 @ public behavior
	 @
	 @ pre R != null;
	 @ pre b != null;
	 @ pre R.isSquare();
	 @ pre R.isUpperTriangular();
	 @ pre b.size() == R.getNbRows();
	 @ pre (* R is nonsingular *);
	 @
	 @ post (* R.times(\result).equals(b) *);
	 @*/
	public Column backSubstitute(Matrix R, Column b) {
		int size = b.size();
		Column result = (Column) b.clone();
		for (int i=size; i >= 1; i--) {
			double bi = result.elementAt(i)/R.elementAt(i,i);
			result.setElementAt(i,bi);
			for (int j=i-1; j>= 1; j--) {
				double bj = result.elementAt(j) - R.elementAt(j,i) * bi;
				result.setElementAt(j,bj);
      }
    }
		return result;
  }

	/**
	 * <p>Solve the lowertriangular linear system of equations defined by
	 * <code>L * x = b</code></p>
	 *
	 * @param L
	 *        The lowertriangular matrix containing the coefficients of the
	 *        equations.
	 * @param b
	 *        A column containing the right-hand sides of the equations.
	 */
 /*@
	 @ public behavior
	 @
	 @ pre L != null;
	 @ pre b != null;
	 @ pre L.isSquare();
	 @ pre L.isLowerTriangular();
	 @ pre b.size() == L.getNbRows();
	 @ pre (* L is nonsingular *);
	 @
	 @ post (* L.times(\result).equals(b) *);
	 @*/
	public Column forwardSubstitute(Matrix L, Column b) {
		int size = b.size();
		Column result = (Column) b.clone();
		for (int i=1; i <= size; i++) {
			double bi = result.elementAt(i)/L.elementAt(i,i);
			result.setElementAt(i,bi);
			for (int j=i+1; j<= size; j++) {
				double bj = result.elementAt(j) - L.elementAt(j,i) * bi;
				result.setElementAt(j,bj);
      }
    }
		return result;
  }

}

/*<copyright>Copyright (C) 1997-2002. This software is copyrighted by 
the people and entities mentioned after the "@author" tags above, on 
behalf of the JUTIL.ORG Project. The copyright is dated by the dates 
after the "@date" tags above. All rights reserved.
This software is published under the terms of the JUTIL.ORG Software
License version 1.1 or later, a copy of which has been included with
this distribution in the LICENSE file, which can also be found at
http://www.jutil.org/LICENSE. This software is distributed WITHOUT 
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 
or FITNESS FOR A PARTICULAR PURPOSE. See the JUTIL.ORG Software 
License for more details.
For more information, please see http://jutil.org/</copyright>*/